1. Field of the Invention
The invention relates to combustion monitoring and control, including anomaly detection and classification, in combustors of gas turbine engines, including by way of example industrial gas turbine (IGT) engines, other types of stationary gas turbine, marine, aero and other vehicular gas turbine engines. More particularly, embodiments of monitoring and control methods and apparatus disclosed herein utilize a common sensing and control system for combustor temperature determination as well as combustion anomaly detection and classification. In embodiments disclosed herein an array of thermoacoustic sensors, acoustic transmitters and/or transceivers are utilized for one or more of real-time active combustor temperature determination, anomaly detection or anomaly classification.
2. Description of the Prior Art
Combustion turbines, such as gas turbine engines, generally comprise a compressor section, a combustor section, a turbine section and an exhaust section. In operation, the compressor section inducts and compresses ambient air. The combustor section generally may include a plurality of combustors for receiving the compressed air and mixing it with fuel to form a fuel/air mixture. The fuel/air mixture is combusted by each of the combustors to form a hot working gas that may be routed to the turbine section where it is expanded through alternating rows of stationary airfoils and rotating airfoils and used to generate power that can drive a rotor. The expanding gas exiting the turbine section can be exhausted from the engine via the exhaust section.
Combustion anomalies, such as flame flashback, have been known to occur in combustion sections of gas turbine engines. Flame flashback is a localized phenomenon that may be caused when a turbulent burning velocity of the air and fuel mixture exceeds an axial flow velocity in the combustor assembly, thus causing a flame to anchor onto one or more components in/around the combustor assembly, such as a liner disposed around the combustion chamber. The anchored flame may burn through the components if a flashback condition remains for extended periods of time without correction thereof. Thus, flame flashback and/or other combustion anomalies may cause undesirable damage and possibly even destruction of combustion engine components, such that repair or replacement of such components may become necessary.
The fuel/air mixture at the individual combustors is controlled during operation of the engine to maintain one or more operating characteristics within a predetermined range, such as, for example, to maintain a desired efficiency and/or power output, control pollutant levels, prevent pressure oscillations and prevent flameouts. In a known type of control arrangement, a bulk turbine exhaust temperature may also be monitored as a parameter that may be used to monitor the operating condition of the engine. For example, a controller may monitor a measured turbine exhaust temperature, and a measured change in temperature at the exhaust may result in the controller changing an operating condition of the engine.
At present, there are several different types of sensors and sensing systems that are being used in the industry for monitoring combustion and maintaining stability of the combustion process for engine protection. For example, dynamic pressure sensors are being used for combustion stability and resonance control. Passive visual (optical visible light and/or infrared spectrum) sensors, ion sensors and Geiger Mueller detectors are used to detect flame on/off in the combustor, while thermocouples are being used for flashback detection.
Particularly, U.S. Pat. No. 7,853,433 detects and classifies combustion anomalies by sampling and subsequent wavelet analysis of combustor thermoacoustic oscillations representative of combustion conditions with sensors, such as dynamic pressure sensors, accelerometers, high temperature microphones, optical sensors and/or ionic sensors. United States Publication No. US2012/0150413 utilizes acoustic pyrometry in an gas turbine exhaust system to determine upstream bulk temperature within one or more of the engine's combustors. Acoustic signals are transmitted from acoustic transmitters and are received by a plurality of acoustic receivers. Each acoustic signal defines a distinct line-of-sound path between a corresponding transmitter and receiver pair. Transmitted signal time-of-flight is determined and processed to determine a path temperature. Multiple path temperatures can be combined and processed to determine bulk temperature at the measurement site. The determined path or bulk temperature or both can be utilized to correlate upstream temperature in the combustor. Co-pending U.S. utility patent application Ser. No. 13/804,132 calculates bulk temperature within a combustor, using a so-called dominant mode approach, by identifying an acoustic frequency at a first location in the engine upstream from the turbine (such as in the combustor) and using the frequency for determining a first bulk temperature value that is directly proportional to the acoustic frequency and a calculated constant value. A calibration second temperature of the working gas is determined in a second location in the engine, such as the engine exhaust. A back calculation is performed with the calibration second temperature to determine a temperature value for the working gas at the first location. The first temperature value is compared to the back calculated temperature value to change the calculated constant value to a recalculated constant value. Subsequent first temperature values at the combustor may be determined based on the recalculated constant value.
Thus, different adverse conditions related to combustion currently require separate sensor designs and/or separate sensing systems to detect those conditions. Known combined gas turbine and other types of gas turbine engine monitoring and control system sensor and detection approaches have not covered all possible adverse combustion fault detections. Installation of different types of disparate sensors and sensing systems in a single gas turbine increases installation cost and maintenance expense. Also, the disparate sensors and sensing systems inherently introduce response lags and delays in the overall gas turbine control system.
Thus, a need exists in the art for an integrated gas turbine monitoring and control system for detecting a broad range of possible combustor failures or, more satisfactorily precursors to faults, during combustion, sharing common sensors and, if desired, a common controller.
Another need exists in the art for an gas turbine active temperature monitoring system that determines actual combustor temperature in real time without the need to obtain reference temperatures from other locations within the engine, such as known bulk temperature systems that back calculate combustor temperature based on temperature measurements obtained in the engine exhaust system.
An additional need exists for an active temperature monitoring system that shares sensors commonly used with gas turbine monitoring and control systems, so that active temperature monitoring can be integrated within the monitoring and control system.